Fibre reinforced plastics (FRP) laminates especially those based on thermosetting resins such as unsaturated polyesters, vinyl esters, epoxides, phenolics, furans and silicones have found wide use in industry. By correct choice of resin type and reinforcement the laminates can be used in the production of pipes, ducts, tanks, vessels for chemical plants, cladding and decorative panels for building, containers, tanks and pipes for potable liquids and foodstuffs, boats, cars and commercial vehicles, railway coaches, and many other applications.
However there are some aggressive environments that attack some or all the resin matrices that are used. This disadvantage has been overcome in some instances by the use of thermoplastics such as rigid polyvinyl chloride, polypropylene or fluorinated ethylene/propylene copolymers as facings to the laminate. Even so there are applications where metals such as aluminum or stainless steel perform better than FRP or FRP with a thermoplastic facing but where the lightness and load bearing properties of FRP would be an advantage.
Very thin sheets of metals (e.g. stainless steel) down to about 0.008 cm thick are now available and many applications can be foreseen where a material of this type with a FRP backing could be used, namely decorative metal faced building panels, metal faced sectional water tanks, metal lined pipes, ducts and tanks and metal faced components for the transport industry. Unfortunately, little or no adhesion can be obtained between stainless steel and thermosetting resins such as standard unsaturated polyesters and vinyl esters even with careful preparation of the stainless steel surface. It has been stated that some resins such as epoxides or polyurethanes are self bonding on to stainless steel (B.P. No. 2,061,834) but these suffer from other disadvantages such as cost (epoxides) and low stiffness (polyurethanes).
We have found a way by which excellent adhesion can be obtained between a metal and those thermosetting resins which are not generally considered as being capable of bonding to metal.